Study on the oxidative stabilization of polyacrylonitrile fibers by microwave heating

A microwave heating method was used for oxidative stabilization of polyacrylonitrile (PAN) fibers. The bulk density, chemical structure (FTIR), crystalline structure (WAXD), and skin-core structure were studied. The results show that the intermolecular cyclization happened above 220 degrees C. From X-ray diffractograms of heat treated fibers, the pre-graphitic structure of stabilized fibers was developed to turbostratic structure. A gradual densification of the fibers occurring was observed after stabilization at a maximum temperature of 240 degrees C. Microwave heating effectively shortened the thermal stabilization process and the thermal stabilization time by 35 min compared with the conventional thermal stabilization process. The skin-core structure of the stabilized fibers was prohibited by microwave heating.